Significant demand for gigabit metropolitan-area networks (MAN) and wide-area networks (WAN) is surfacing and several experimental networks are in the process of being implemented. These networks use electronic repeaters to regenerate the signal at each node before further retransmission. Regenerative repeaters, however, impose performance and reliability constraints due to the electronic processing at each node, which thus limits the operating data rates of the network. Further, a single component failure may compromise the integrity of the entire network. Moreover, these topologies rely on technology that still needs significant improvement.
For gigabit networks without repeaters, considerable interest has been focused on wavelength division multiplexed (WDM) star networks as described in "Dense Wavelength Division Multiplexing Networks: Principles and Applications" by Charles A. Brackett in the IEEE Journal on Selected Areas in Communications, Vol. 8, No. 6. August 1990, and most recently ring networks using distributed optical amplification as described in "Optical Ring Networks with Distributed Amplification" by Evan Goldstein in IEEE Photonics Technology Letters, Vol. 3, No. 4, April 1991.
Dual bus networks, using a Distributed Queue Dual Bus (DQDB) protocol as described in Distributed Queue Dual Bus Subset of a Metropolitan Area Network, IEEE, New York, July 1990 are an attractive choice for MAN and WAN environments because of excellent network survivability and flexibility. DQDB networks have shown quite efficient operations even when the data rate is high or the propogation delay over the network is large.
The IEEE 802.6 standard using the Distributed Queued Dual Bus (DQDB) architecture is emerging as an international standard for MAN with data rates up to 155 Mb/s. However, a repeater-less multigigabit dual bus network with optical amplifiers and passive fiber access for MAN and WAN is desirable in order to support a large number of nodes for connectionless data services, spread over a wide geographic area, with use of currently available technology.